Cambodia, country on the Indochinese mainland of Southeast Asia. Cambodia is largely a land of plains and great rivers and lies amid important overland and river trade routes linking China to India and Southeast Asia. The influences of many Asian cultures, alongside those of France and the United States, can be seen in the capital, Phnom Penh, one of a handful of urban centres in the largely rural country.

For 2,000 years Cambodia’s civilization absorbed influences from India and China and, in turn, transferred them to other Southeast Asian civilizations. From the Hindu-Buddhist kingdoms of Funan and Chenla (1st–8th century) through the classical age of the Angkor period (9th–15th century), it held sway over territories that are now part of Thailand, Vietnam, and Laos. The Khmer (Cambodian) empire reached its apex in the 12th century, a time marked by the construction of the massive temple complexes known as Angkor Wat and Bayon and the imperial capital of Angkor Thom. Following 400 years of decline, Cambodia became a French colony and during the 20th century experienced the turmoil of war, occupation by the Japanese, postwar independence, and political instability. Between 1975 and 1979 the country was devastated by the reign of the Khmer Rouge, a rural communist guerrilla movement. During the Khmer Rouge’s period of power, at least 1.5 million Cambodians were killed or died, a monumental tragedy from which the country still suffers.

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Cambodia began the process of recovery under the Vietnam-backed regime of the People’s Republic of Kampuchea (1979–89), and in the 1990s it regained political autonomy, reestablished a constitutional government, and subsequently instituted free elections. The Cambodian economy has steadily improved, and the country seems to be living by the words of the Cambodian proverb, "Fear not the future, weep not for the past."

Land

Cambodia, about one-third the size of France and somewhat larger than the U.S. state of Missouri, is bordered to the west and northwest by Thailand, to the northeast by Laos, to the east and southeast by Vietnam, and to the southwest by the Gulf of Thailand. The country’s maximum extent is about 280 miles (450 km) from north to south and 360 miles (580 km) from east to west.

Relief

Cambodia’s landscape is characterized by a low-lying central alluvial plain that is surrounded by uplands and low mountains and includes the Tonle Sap (Great Lake) and the upper reaches of the Mekong River delta. Extending outward from this central region are transitional plains, thinly forested and rising to elevations of about 650 feet (200 metres) above sea level. To the north the Cambodian plain abuts a sandstone escarpment, which forms a southward-facing cliff stretching more than 200 miles (320 km) from west to east and rising abruptly above the plain to heights of 600 to 1,800 feet (180 to 550 metres). This escarpment marks the southern limit of the Dangrek (Khmer: Dângrêk) Mountains. Flowing south through the country’s eastern regions is the Mekong River. East of the Mekong the transitional plains gradually merge with the eastern highlands, a region of forested mountains and high plateaus that extend into Laos and Vietnam. In southwestern Cambodia two distinct upland blocks, the Krâvanh (Cardamom) Mountains and the Dâmrei (Elephant) Mountains, form another highland region that covers much of the land area between the Tonle Sap and the Gulf of Thailand. In this remote and largely uninhabited area, Mount Aôral, Cambodia’s highest peak, rises to an elevation of 5,949 feet (1,813 metres). The southern coastal region adjoining the Gulf of Thailand is a narrow lowland strip, heavily wooded and sparsely populated, which is isolated from the central plain by the southwestern highlands.

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Krâvanh Mountains, southwestern Cambodia.

Paul Mason/U.S.Agency for International Development

Drainage

The two dominant hydrological features of Cambodia are the Mekong River and the Tonle Sap. Rising in the Plateau of Tibet and emptying into the South China Sea, the Mekong enters Cambodia from Laos at the Khone Falls and flows generally southward to the border with Vietnam, a distance within Cambodia of approximately 315 miles (510 km). The Mekong is connected to the Tonle Sap by the Sab River. During the rainy season (mid-May to early October), the Mekong’s enormous volume of water backs up into the Sab and flows up into the Tonle Sap 65 miles (105 km) to the northwest, expanding the lake’s surface area from a dry-season minimum of 1,200 square miles (3,100 square km) to a rainy-season maximum of more than 3,000 square miles (7,800 square km). As the water level of the Mekong falls during the dry season, the process is reversed: water drains from the Tonle Sap back down into the Mekong, switching the direction of its flow. As a result of this annual phenomenon, the Tonle Sap is one of the world’s richest sources of freshwater fish.

Soils

Most of Cambodia’s soils are sandy and poor in nutrients. The so-called red-soil areas in the eastern part of the country, however, are suitable for commercial crops such as rubber and cotton. The annual flooding of the Mekong during the rainy season deposits a rich alluvial sediment that accounts for the fertility of the central plain and provides natural irrigation for rice cultivation.

In the southwestern part of the Indochinese peninsula of Southeast Asia lies the country of Cambodia. Modern Cambodia is a remnant of the powerful Khmer Empire, which at its height from the 11th to the 13th century ruled much of what is now Vietnam, Laos, and Thailand. In more recent times Cambodia has endured great turmoil-French colonization, the genocidal regime of the Khmer Rouge, and Vietnamese occupation. In the 1990s Cambodia finally regained a measure of political stability and began to recover from decades of conflict. The capital of Cambodia is Phnom Penh. Area 69,898 square miles (181,035 square kilometers). Population (2015 est.) 15,405,000.